Pure drinking water includes water drawn from the ordinary uncontaminated sources of the spring, the well or the running stream. Such water contains always the essential gases of the atmosphere in solution with greater or less quantities of carbon dioxid, traces of other gases, traces of common salt, of lime, of magnesia, of soda, of iron, and many other mineral substances. It is free from any excess of organic matter, of ammonia or nitric acid, nitrous acid, and chlorin derived from any other source than common salt. It will hardly be contested by physiologists and hygienists that water of this description properly handled is better for constant use as a beverage than any of the other forms of water described. In general, therefore, the term "pure water" may be applied to water which does not carry any diseases, is free from contamination with sewage or excreta, and carries only a moderate amount of harmless and even helpful natural mineral constituents.